a
Institute of Advanced Materials and Technology, University of Science and Technology Beijing, Beijing 100083, China
E-mail:fanlizhen@ustb.edu.cnFax: +86-10-62334311 Tel: +86-10-62334311

Abstract

Corncob sponge is a type of agricultural abandoned byproduct and abundant around the world. Herein, a facile one-pot carbonization and activation method is developed to convert corncob sponge into three-dimensional (3D) interconnected honeycomb-like porous carbon, followed by an effective binary-heteroatom doping to fabricate nitrogen and sulfur co-doped activated corncob sponge (denoted as N,S-ACS). The resultant products possess a high accessible surface area (1874 m2 g−1) induced by the 3D honeycomb-like framework and a highly porous structure that benefits a large ion storage and a rapid ion transfer. In addition to the electrical double layer capacitance, heteroatom doping evokes faradic contribution. N,S-ACS demonstrates a remarkable specific capacitance of 404 and 253 F g−1 at the current densities of 0.1 and 10 A g−1 in a 6 mol L−1 KOH electrolyte, respectively, along with a high cycling stability with only 1% loss over 10 000 cycles. Furthermore, the assembled symmetric flexible solid-state supercapacitors with the electrode of N,S-ACS and the electrolyte of a PVA/KOH gel display a high integrated energy–power density of 30 W h kg−1 at 8 kW kg−1 and a 99% capacitance retention after 10 000 cycles at 3 A g−1. The fascinating performance significantly endows N,S-ACS with great prospects as a supercapacitor electrode.

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